Weco filter media bags come in both coarse and fine mesh sizes. The zipper on the bags is made from aluminium, so you do not need to worry about rust problems or problems with a plastic zipper breaking down.
Rivers to Reef says: We use these bags in the shop and really like their quality. We have used some of the bags in our saltwater sumps for years and the are still in great working condition. We like zipper bags over drawstring as we feel it keeps the media in better. It used to have to be drawstring all the time, especially in saltwater, but the aluminum zipper holds up well without any corrosion.